1. Field of the Invention
The present invention relates to an apparatus for heating and ventilating vehicle compartments or the like, and comprises: a housing having an air inlet for recirculated air and/or fresh air; a blower; a heat exchanger; and an air outlet or discharge; whereby a secondary air passage or duct is arranged parallel to the heat exchanger, and a mixing chamber for both air flows is provided in the outlet or discharge region.
2. Description of the Prior Art
With one known apparatus of this general type (see German Offenlegungsschrift No. 29 36 058), several blowers are arranged side by side and charge a common space or chamber with recirculating air and/or fresh air; several heat exchangers, likewise arranged side by side, adjoin the space or chamber. Secondary air ducts are provided on both sides of the heat exchangers between these heat exchangers and the walls of the housing of the apparatus. If one blower and one heat exchanger is considered in the flow path, there thus results that a single blower acts not only on the heat exchanger, but also on the secondary air duct with fresh air and/or recirculating air. The two flows are mixed downstream from the heat exchanger, whereby a constant mixing ratio results. The temperature control with the known arrangement is effected by providing a valve in the circulation of the heating medium, e.g. cooling water or cooling oil, of an internal combustion engine; by means of this valve, the heating medium can adjustably act upon the heat exchanger. Such valves, with their adjustment members, are costly and susceptible to disturbance, so that already after a short time of operation there exists the danger that the heat exchanger or heat exchangers no longer operate completely satisfactorily.
Additionally, it is known to provide adjustable flaps or valves in the secondary air duct or ducts of a heat exchanger acted upon by a blower; these flaps or valves, however, primarily make possible a volume control of the supplied air. The flaps or valves also must be provided with adjustment members, resulting in a considerable constructional cost. Additionally, the adjustment members are susceptible to disturbance. Finally, a linear air volume change can be achieved with the flaps or valves only at considerable cost and complexity, since the opening angle of the flaps or valves is not proportional to the air volume flowing therethrough. Furthermore, valves for temperature control are necessary in the circulation of the heating medium. A sensitive, constant temperature control over longer operating times of the vehicle is thereby made more difficult.